How do molecules and atoms exert force (or pressure)?

Answer 1

just like the way you do pushups, or you nudge your friend. you also feel something pushing you back, it's the Newton's Law, force action = force reaction

Answer 2

All atoms and molecules have a certain element of motion, which increases with temperature (see ideal gas equation pV=NRT) - for example, in a gas filled balloon, the pressure on the insides of the balloon is due to the collisions of the gaseous particles (molecules) with the walls of the container (the balloon). If the temperature of the gas in the container increases, the motion of the molecules increases increasing the likelihood and frequency of molecule-wall collisions and hence increasing the pressure.
Similarly, intermolecular collisions cause liquids to exert force (you can feel a weight of water in your hand). The more dense the substance the more likely the collision (more molecules per volume unit), so you can feel weight of water but not so much with water vapor.
Capisce?

Answer 3

molecules of an atom exert force due to the effect of heat. For instance when an iron rod is heated,expansion takes place, this is because the molecules/atoms of the rod gain kinetic energy in exposure to heat,thus they exert force or pressure which leads to the increase in the size of the rod (expansion).

Answer 4

Heat gives the atoms and molecules energy. This translates into kinetic energy as they move around. Using the laws of physics, F=ma. Force = mass x acceleration.

If this force hits the sides of a container, it is converted nto pressure, which is force per unit of area.